you can do this by using view modes in eZ publish. Every object/node can be viewed in many different ways, the default is the full mode and will have the url /content/view/full/42 where 42 is your current node id. What you can do is to create a view mode /content/view/showcomments/42. Then you need to create an override template for your class and that viewmode. E.g. create the file design/standard/templates/node/view/showcomments.tpl and in this file you will list the comments, while in the default-full- you don't.
